Monitoring for water safety can be greatly improved to prevent accidents, particularly involving children, by accurate and immediate notification of a water accident. This is critical since a drowning death can occur in just a few minutes. Reliability to accurately detect water immersion is essential. If a child has fallen into water, any time delay threatens the child's life. A false alarm from a monitoring system is acceptable, if there is assurance that a positive water emergency will not go undetected. However, false alarms cannot be so frequent that the alarm fails to initiate an urgent response. The sensitivity of the monitoring system should be settable such that incidental wetting from sprinklers, taps, splash, rain or perspiration does not trigger the alarm.
In addition, to be effective as a monitor for children, the transmitter must be securely fastened to the child and resistant to tampering. A casing which opens to facilitate battery replacement can be opened by a child and disabled without intent, and without the knowledge of the supervising adult. Waterproof circuitry for electrical water safety devices generally comprises hermetically coated wires and water sealed containers. The use of a single printed circuit board is attractive since no leads can be inadvertently disconnected by a child.
U.S. Pat. No. 5,408,222 issued Apr. 18, 1995 by Yacob Yaffe et al. discloses a timing means that allows an alarm to sound after immersion in fluid for a determined interval. This may be useful for monitoring weak swimmers, but immersion of a non-swimmer must be responded to immediately. A timing delay of emergency response increases the risk of the child drowning or suffering other immersion injury such as brain damage. The device includes a sensor, a timing circuit and a transmitter that is activated in response to a 40-60 second immersion time. An antenna comprises a wire lead incorporated in a securing headband. The structure of the circuitry is not as compact and tamper resistant as a printed circuit. The device is also not sensitive to distinguish incidental wetness from immersion.
A further patent U.S. Pat. No. 4,918,433 issued Apr. 17, 1990 to Robert Moore discloses a belt mounted transmission monitor. In a horizontal position the sensors are shielded from falling water such as rain, etc. The sensors do not have a settable threshold to indicate a level of wetness. Like the headband device, the belt circuitry is rather large carrying a separate transmitter unit and is not as resistant to tampering with leads as a printed circuit board.
A more complex system is disclosed in U.S. Pat. No. 5,650,770 issued Jul. 22, 1997 to Dan Schlager et al. comprising a monitoring system for location surveillance by GPS or distance detection as well as a variety of hazard sensors including an immersion sensor. The system includes a panic button for the user to alert the base station. For child safety, an alarm needs to be automatic. Because the device transmits a status regularly, the greater power demand requires a larger battery and a larger device. The complexity, cost and size are beyond the needs of most users for backyard safety. A simple, reliable, compact and economical device is needed.
It is an object of the invention to provide a monitoring system for detecting a child's immersion in water which is reliably automatic, resistant to false alarm and resistant to tampering or damage which would disable the system.
It is a further object to provide a low energy system that provides reliable response over a long use period.